Steam Water Separator Wetting Device for Thermal Stress Reduction

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Solution Overview

Problem

Steam generators experience uneven expansion and contraction of vessel walls due to differing heat transfer coefficients between steam and water, leading to mechanical stresses and potential failure during frequent start-ups and shut-downs, particularly in solar power installations where heating is intermittent.

Innovation Solution

A steam water separator with a wetting device that creates a water film or layer on the inner surface of the vessel wall in the steam zone, equalizing the heat transfer coefficient and imposed medium temperature across the vessel wall, thereby reducing uneven expansion and contraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the vessel is heated frequently for start-up and shutdown, then the steam generator can adapt to intermittent solar energy availability, but the vessel wall experiences uneven expansion and contraction leading to mechanical stresses and potential failure

Engineering Contradiction:

Improveadaptability to intermittent solar energyVSAvoidvessel wall reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention applies a water film specifically to the steam zone inner surface of the vessel wall, creating a localized thermal management solution. This water film layer is not present throughout the entire vessel but specifically in the region where steam contacts the wall, addressing the local thermal imbalance problem caused by differential heat transfer coefficients between steam and water zones.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The water film acts as an intermediary layer between the steam and the vessel wall in the steam zone. This intermediate water layer mediates the heat transfer process, equalizing the thermal conditions at the wall surface and preventing the direct high-temperature steam from causing localized rapid expansion and mechanical stress.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the steam zone wall heats up faster during start-up, then steam generation can begin quickly, but the vessel bends over its longitudinal axis causing drum humping and mechanical stresses

Engineering Contradiction:

Improvesteam generation speedVSAvoidvessel shape stability

Core Design Contradiction:

SpeedVSShape

Solution Approach 1:

The invention changes the thermal parameter at the vessel wall surface by introducing a water film, which modifies the heat transfer coefficient and temperature distribution. This parameter change equalizes the thermal conditions between the steam zone and water zone walls, preventing differential expansion that would cause vessel bending and drum humping while still allowing rapid steam generation.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If the heat transfer coefficient between steam and vessel wall is higher, then steam heating is more efficient, but the vessel wall expands unevenly compared to the water zone wall

Engineering Contradiction:

Improvesteam heating efficiencyVSAvoidvessel wall uniform expansion

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The water film serves as an intermediary that modifies the heat transfer characteristics at the steam-zone vessel wall interface. By introducing this water layer, the heat transfer coefficient is adjusted to match that of the water zone, creating uniform thermal conditions across the entire vessel wall surface and ensuring stable, uniform expansion during heating operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution significantly reduces mechanical stresses and the likelihood of vessel bending, enhancing the durability and reliability of steam generators by ensuring even thermal expansion and contraction across the vessel wall.

Implementation Method 1

the heat transfer coefficient and imposed medium temperature are substantially equal over the inner surface of the vessel wall in the water zone and the steam zone

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

the expansion of the vessel wall during start-up and the contraction of the vessel wall during turning down of the process will be substantially similar over the vessel wall

Methodology Applied

Scientific EffectThermal equilibrium: Thermal Expansion

Data Source

PatentUS9851097B2Steam water separator, use of such water steam separator, and method for separating steam and water

Publication Date: 2017.12.26 NEM ENERGY

AI summary

A steam water separator includes: —a vessel having a vessel wall delimiting an interior of the vessel, where the vessel is configured to contain steam in a steam zone and water in a water zone in the interior of the vessel, —at least one inlet for introducing steam and/or water in the vessel, —at least one steam outlet for taking steam out of the vessel, —at least one water outlet for taking water out of the vessel, and a wetting device configured to wet in the steam zone an inner surface of the vessel wall.